The general and long-term goal of my laboratory is to study autoantibody- mediated skin diseases in order to further our understanding not only of the pathophysiology of these diseases but also of the structure and function of normal epidermis and epidermal basement membrane zone. Specifically, antibodies in these diseases define molecules in the normal epidermis. We are characterizing, at an immunochemical and molecular biologic level, the antigens defined by three of these diseases: bullous pemphigoid (BP), pemphigus vulgaris (PV), and pemphigus foliaceus (PF). BP antigen is known to be a component of the hemidesmosome, a basal cell-substrate adhesion junction. With extension cDNA cloning, using a previously-isolated partial cDNA, we have cloned overlapping cDNAs encoding almost the total BP antigen molecule. Analysis of protein structure and amino acid sequence indicates marked homology with desmoplakin I, a desmosome plaque protein. These studies indicate that BP antigen and desmoplakin I form a gene family of adhesion plaque proteins. We are now using the polymerase chain reaction (PCR) for the rapid amplification of cDNA ends (RACE) to finish cloning the 5' end of the cDNA. In addition, we have begun characterization of the BP antigen gene in normal humans, animals, and patients with junctional epidermolysis bullosa, a disease with abnormal hemidesmosomes. With immunochemical methods we have defined a new form of pemphigus, paraneoplastic pemphigus, that is clinically, histologically, and molecularly unique. Finally, we have started cDNA cloning of the PV antigen by antibody screening of a lambda-gtll expression cDNA library derived from cultured keratinocytes. We are raising antibodies against fusion proteins derived from this cDNA. These should prove useful for studying, localization of the PV antigen as well as pathophysiology of disease.